U.S. patent number 7,462,224 [Application Number 11/304,216] was granted by the patent office on 2008-12-09 for array of shaped activated carbon articles for tank venting systems and motor vehicles.
This patent grant is currently assigned to Helsa-Automotive GmbH & Co. KG. Invention is credited to Thomas Wolff.
United States Patent |
7,462,224 |
Wolff |
December 9, 2008 |
Array of shaped activated carbon articles for tank venting systems
and motor vehicles
Abstract
The invention relates to an array of shaped activated carbon
articles having channels extending through said array of shaped
activated carbon articles, wherein said array of shaped activated
carbon articles includes at least two shaped monolithic activated
carbon articles containing channels, which channels of the at least
two shaped monolithic activated carbon articles are connected so as
to communicate with each other and the free cross-sectional areas
formed by the channel cross-sections thereof have different values
in said first and second shaped monolithic activated carbon
articles. The invention also relates to a tank venting system and a
motor vehicle containing an array of shaped activated carbon
articles of the invention. Finally, the invention relates to a
process for the production of said array of shaped activated carbon
articles of the invention.
Inventors: |
Wolff; Thomas (Munchberg,
DE) |
Assignee: |
Helsa-Automotive GmbH & Co.
KG (Gefrees, DE)
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Family
ID: |
36599332 |
Appl.
No.: |
11/304,216 |
Filed: |
December 15, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060142154 A1 |
Jun 29, 2006 |
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Foreign Application Priority Data
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Dec 23, 2004 [DE] |
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10 2004 063 434 |
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Current U.S.
Class: |
96/132;
123/519 |
Current CPC
Class: |
B01D
53/0407 (20130101); C01B 32/382 (20170801); F02M
25/0854 (20130101); B01D 2253/102 (20130101); B01D
2253/342 (20130101); Y10T 29/49826 (20150115); B01D
2259/4516 (20130101) |
Current International
Class: |
F02M
33/02 (20060101); B01D 53/04 (20060101) |
Field of
Search: |
;96/108,121,131,132,134,147 ;123/518-520 ;502/416 ;428/116,118 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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199 52 092 |
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Oct 2000 |
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DE |
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101 04 882 |
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Aug 2002 |
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DE |
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101 50 062 |
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Feb 2003 |
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DE |
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102 13 016 |
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Oct 2003 |
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DE |
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1 200 343 |
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Oct 2003 |
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EP |
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1514588 |
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Mar 2005 |
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EP |
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1541817 |
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Jun 2005 |
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EP |
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WO 00/78138 |
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Dec 2000 |
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WO |
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WO 01/62367 |
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Aug 2001 |
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WO |
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Other References
Greil et al., "Effect of microstructure on the fracture behavior of
biomorphous silicon carbide ceramics", Journal of the European
Ceramic Society, 2002, 2697-2707, vol. 22(14-15). cited by
other.
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Primary Examiner: Lawrence; Frank M
Attorney, Agent or Firm: Fulbright & Jaworski, LLP
Claims
What is claimed is:
1. An array of shaped activated carbon articles having channels
extending through said array of shaped activated carbon articles,
said array comprising: at least three shaped monolithic activated
carbon articles containing channels, in which the channels are
arranged so as to communicate with each other and the free
cross-sectional area formed by the channel cross-sections increases
in size in consecutive monolithic activated carbon articles.
2. An array of shaped activated carbon articles as defined in claim
1, wherein the content of activated carbon in the shaped activated
carbon articles is at least 75% by weight, based on the total
weight of the shaped activated carbon articles.
3. An array of shaped activated carbon articles as defined in claim
1, wherein the content of activated carbon in the shaped activated
carbon articles is at least 80% by weight based on the total weight
of the shaped activated carbon articles.
4. An array of shaped activated carbon articles as defined in claim
1, wherein the content of activated carbon in the shaped activated
carbon articles is at least 95% by weight based on the total weight
of the shaped activated carbon articles.
5. An array of shaped activated carbon articles as defined in claim
1, wherein said channels in said shaped activated carbon articles
extend substantially parallel to each other and substantially
parallel to the longitudinal axis of said shaped activated carbon
article.
6. An array of shaped activated carbon articles as defined claim 1,
wherein said channels independently exhibit a cross section
selected from a group consisting of trigonal, tetragonal, square,
pentagonal, hexagonal, octogonal, spherical, and oval
cross-section.
7. An array of shaped activated carbon articles as defined in claim
1, wherein the free cross-sectional area formed by the channel
cross sections increases in size in consecutive monolithic shaped
activated carbon articles by from 5% to 60%.
8. An array of shaped activated carbon articles as defined in claim
1, wherein the free cross-sectional area formed by the channel
cross sections in a first shaped monolithic activated carbon
article is from 10% to less than 35%.
9. An array of shaped activated carbon articles as defined in claim
1, wherein the free cross-sectional sectional area formed by the
channel cross sections in a second shaped monolithic activated
carbon article is from 35% to not more than 60%.
10. An array of shaped activated carbon articles as defined in
claim 1, wherein the free cross-sectional area formed by the
channel cross sections in a third shaped monolithic activated
carbon article is from more than 60% to less than 80%.
11. An array of shaped activated carbon articles as defined in
claim 1, wherein the cross-sectional diameters of said channels
range from 0.1 mm to 7 mm.
12. An array of shaped activated carbon articles as defined in
claim 1, wherein the walls separating said channels have a
thickness ranging from 0.5 mm to 10 mm.
13. An array of shaped activated carbon articles as defined in
claim 1, wherein said array of shaped activated carbon articles
exhibits a ratio of length to cross-sectional diameter of at least
3:1.
14. An array of shaped activated carbon articles as defined in
claim 1, wherein each shaped activated carbon article exhibits an
incremental adsorption capacity of more than 35 g/l at levels of
n-butane in air of from 5% by volume to 50% by volume.
15. An array of shaped activated carbon articles as defined claim
1, wherein said shaped activated carbon articles in the array of
shaped activated carbon articles are disposed abutting each other
or at a distance from each other.
16. A tank venting system, comprising: an array of shaped activated
carbon articles having at least three shaped monolithic activated
carbon articles containing channels, in which the channels are
arranged so as to communicate with each other and the free
cross-sectional area formed by the channel cross-sections increases
in size in consecutive monolithic activated carbon articles.
17. A tank venting system as defined in claim 16, wherein the
venting system contains an activated carbon packing in addition to
said array of shaped activated carbon articles.
18. An array of shaped activated carbon articles as defined in
claim 1, wherein the content of activated carbon in the shaped
activated carbon articles is at least 90% by weight based on the
total weight of the shaped activated carbon articles.
19. An array of shaped activated carbon articles as defined in
claim 1, wherein the content of activated carbon in the shaped
activated carbon articles is at least 98% by weight on the total
weight of the shaped activated carbon articles.
20. An array of shaped activated carbon articles as defined in
claim 7, wherein the free cross-sectional area formed by the
channel cross sections increases in size in consecutive monolithic
shaped activated carbon articles by from 10% to 50%.
21. An array of shaped activated carbon articles as defined in
claim 8, wherein the free cross-sectional area formed by the
channel cross sections in a first shaped monolithic activated
carbon article is from 20% to 30%.
22. An array of shaped activated carbon articles as defined in
claim 9, wherein the free cross-sectional area formed by the
channel cross sections in a second shaped monolithic activated
carbon article is from 40% to 55%.
23. An array of shaped activated carbon articles as defined in
claim 10, wherein the free cross-sectional area formed by the
channel cross sections in a third shaped monolithic activated
carbon article is from 65% to 75%.
24. An array of shaped activated carbon articles as defined in
claim 11, wherein the cross-sectional diameters of said channels
range from 0.5 mm to 4.5 mm.
25. An array of shaped activated carbon articles as defined in
claim 12, wherein the walls separating said channels have a
thickness ranging from 0.8 mm to 5 mm.
26. An array of shaped activated carbon articles as defined in
claim 13, wherein said array of shaped activated carbon articles
exhibits a ratio of length to cross-sectional diameter of at least
4:1.
27. An array of shaped activated carbon articles as defined in
claim 26, wherein said array of shaped activated carbon articles
exhibits a ratio of length to cross-sectional diameter of at least
6:1.
28. An array of shaped activated carbon articles as defined in
claim 27, wherein said array of shaped activated carbon articles
exhibits a ratio of length to cross-sectional diameter of at least
8:1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to German application DE
102004063434.3 filed Dec. 23, 2004.
TECHNICAL FIELD
The invention relates to a shaped activated carbon article and to a
process for the production thereof. In addition, the invention
relates to a tank venting system and to a motor vehicle.
BACKGROUND OF THE INVENTION
Shaped activated carbon articles are used in the automobile
industry, in particular in tank venting systems, for the reduction
of evaporative emissions from a motor fuel supply system.
Hydrocarbons emitted by a motor fuel reservoir as a result of an
increase in pressure, particularly when the motor vehicles are not
in motion and are exposed, for example, to direct solar radiation
in the summer months, are retained by such tank venting systems to
prevent such emissions from passing into the environment.
The tank venting systems or tank venting filters can consist of
single-chamber or multi-chamber systems having activated carbon
packings. Twin-chamber systems are disclosed in U.S. Pat. No.
5,957,114 or U.S. Pat. No. 6,503,301.
DE 199 52 092 C1 discloses an activated carbon filter which
comprises a filter section containing activated carbon and a filter
layer of high capacity adsorbent containing a material comprising
zeolite and/or silica gel and/or alumina and/or
divinylbenzenestyrene.
WO 01/62367 discloses a method for the adsorption of hydrocarbon
vapors from motor fuel gas mixtures, in which the gas mixture is
initially passed through a first adsorption system and then through
a second adsorption system, and in which the adsorption rate of the
second adsorption system is higher than the adsorption rate of the
first adsorption system. The first and second adsorption systems
can both consist of activated carbon, the surface area to volume
ratio of which differs in the two systems.
The aforementioned filter systems all use activated carbon
packings, which suffers from the drawback that they all show a very
high pressure drop.
In order to achieve good regenerability of activated carbon
packings, the particle size of the activated carbon used must be as
small as possible. The use of activated carbon of such minimum size
leads adversely to an even greater pressure drop in the
aforementioned systems.
If a tank venting system or a tank venting filter is to show a low
pressure drop combined with good regenerability, use must be made
of monolithic structures containing an adsorbent.
U.S. Pat. No. 4,386,947 discloses a device for the adsorption of
motor fuel vapors, in which first, second and third monolithic
structures comprising activated carbon are laminated together such
that the passages in the monolithic structures form a zigzag path,
through which the gas or vapor is passed. This arrangement is too
complicated for normal manufacturing technology and too
cost-intensive in regard of the fact that the tank venting systems
are mass products.
U.S. Pat. No. 6,540,815 B1 discloses a method for the reduction of
motor fuel vapors in automobiles, in which the vapors are passed
initially through an activated carbon packing and subsequently
through an activated carbon-containing shaped ceramic article
having a honeycomb structure. The method disclosed in U.S. Pat. No.
6,540,815 B1 suffers from the disadvantage that, on the one hand,
an activated carbon packing must be used, which, as explained
above, produces a high pressure drop, and, on the other hand, the
activated carbon-containing ceramic honeycomb filter contains not
more than approximately 35% by weight of activated carbon on
account of the content of ceramics material and consequently has a
restricted adsorptive capacity.
A further disadvantage arising when use is made of activated carbon
packings in a motor vehicle is that when the motor vehicle is in
motion the activated carbon packing is subjected to vibrations
causing the activated carbon particles to rub against one another.
The rubbing of the activated carbon particles against one another
produces abrasion and leads to pulverization of the activated
carbon, whereby the adsorptive capacity of the activated carbon
packing is impaired.
It is an object of the invention to provide an adsorbent,
preferably for the adsorption of hydrocarbon vapors, in a form
which enables a good adsorptive capacity to be combined with a low
pressure drop.
BRIEF SUMMARY OF THE INVENTION
The object underlying the invention is achieved by providing an
array of shaped activated carbon articles having channels extending
through said array of shaped activated carbon articles, which array
of shaped activated carbon articles contains at least two shaped
monolithic activated carbon articles having channels, which
channels of the at least two shaped monolithic activated carbon
articles are connected so as to communicate with one another and
the free cross-sectional areas formed by the channel cross sections
differ in said first and second shaped monolithic activated carbon
articles.
Preferred embodiments of the invention are specified in the
subclaims.
The object underlying the invention is furthermore achieved by
providing a process for the production of an array of shaped
activated carbon articles according to the invention, comprising
the following steps:
(a) blending carbon particles, binder, liquid phase, and optionally
further auxiliaries to provide an extrudable composition,
(b) extruding the composition obtained in step (a) to give shaped
monolithic articles having channels,
(c) drying the shaped articles obtained in step (b),
(d) carbonizing the dried shaped articles to produce shaped carbon
articles,
(e) optionally activating the carbonized shaped carbon
articles,
(f) arranging at least two shaped activated carbon articles, in
which the free cross-sectional areas formed by the channel
cross-sections differ from each other, in such a manner that the
channels of the at least two shaped activated carbon articles are
connected so as to communicate with one another.
For the purposes of the invention, the term "carbon particles" is
understood as meaning particles of carbon and carbon-containing
particles. That is to say, the particles can also contain other
constituents in addition to carbon. These other constituents are
preferably pyrolyzed and/or converted to carbon during
carbonization.
Preferably, the carbon particles consist mainly of carbon material,
and more preferably the carbon particles consist almost entirely of
carbon material. Very preferably, the carbon particles consist
exclusively of carbon material. The starting material can be coke
from all kinds of parent substance, for example wood, peat, stone
fruit kernels, nutshells, anthracite, and/or lignite.
According to a further preferred embodiment, the carbon material
used is activated carbon.
Activation according to step (e) is preferably only carried out if
the carbon particles used are not activated carbon particles. That
is to say, activation according to step (e) is not necessary if
activated carbon is used as the carbon particles.
The shaped monolithic activated carbon articles are preferably
obtained by extrusion, and consequently exhibit an elongated form.
During the production of the shaped monolithic activated carbon
articles by extrusion, the resulting extrudate can be cut to length
as required. The channels present in the shaped monolithic
activated carbon article preferably extend substantially parallel
to one another. Furthermore it is preferred that the channels
extend substantially parallel to the longitudinal axis of the
shaped monolithic activated carbon article. The channels in this
case preferably extend right through the shaped activated carbon
article, i.e., for example, from a first end face normal to the
longitudinal axis of the shaped activated carbon article up to a
second such face. The shaped monolithic activated carbon article
can in this case be in the form of a cuboid or a cylinder. The
geometry of the cross-section normal to the longitudinal axis of
the shaped monolithic activated carbon article can be trigonal,
tetragonal, preferably square, pentagonal, hexagonal, octagonal,
decagonal, round, or oval. Basically, any desired external geometry
of the shaped monolithic activated carbon articles can be used to
allow for the particular spatial conditions in, for example, a
motor vehicle.
The channels of the at least two shaped monolithic activated carbon
articles are connected so as to communicate with one another. That
is to say, gases or vapors can pass from the channels of a first
shaped monolithic activated carbon article to the channels of a
second shaped monolithic activated carbon article. If the array of
shaped activated carbon articles consists of more than two shaped
monolithic activated carbon articles, for example of three, four,
five or more shaped monolithic activated carbon articles, all
channels of these shaped monolithic activated carbon articles will
be connected so as to communicate with one another, such that the
gases or vapors will pass successively through the channels of all
succeeding shaped monolithic activated carbon articles so as to
cause a depletion of pollutants, for example a depletion of
hydrocarbons, in the air.
The channels of the two, three, four, five, or more successively
arranged shaped monolithic activated carbon articles can in this
case be arranged directly abutting one another. For example, it is
possible for the end faces of the various shaped monolithic
activated carbon articles to be arranged directly abutting one
another.
The shaped monolithic activated carbon articles can in this case be
glued or joined to one another by means of adhesives, for example
by means of adhesives applied to the end faces. Alternatively
however, the shaped activated carbon articles may be arranged
successively in an envelope, for example in a shrinkage tube or a
housing, in which case the end faces of the shaped monolithic
activated carbon articles can again be arranged abutting one
another. Of course, it is also possible for the shaped monolithic
activated carbon articles to be arranged at a distance from one
another. For example, the shaped monolithic activated carbon
articles can be arranged in a shrinkage tube such that the
shrinkage tube contracts between two adjacently arranged shaped
monolithic activated carbon articles and a gas-tight or vapor-tight
connection forms between the adjacent shaped monolithic activated
carbon articles. The two, three, four, or more shaped monolithic
activated carbon articles can also be arranged at a distance from
one another in a gas-tight or vapor-tight housing. In this case,
the shaped monolithic activated carbon articles can be arranged
parallel to one another in such a housing for the purpose of saving
space.
The free cross-sectional areas of the first and second shaped
monolithic activated carbon articles have different values. The
free cross-sectional area is formed by the sum of the
cross-sectional areas of the channels in a cross-section normal to
the longitudinal axis of the shaped activated carbon article.
According to a preferred embodiment, the activated carbon content
in the shaped activated carbon articles is at least 75% by weight,
based on the total weight of the shaped activated carbon articles.
Furthermore, the activated carbon content is preferably at least
80% by weight, more preferably at least 90% by weight, very
preferably at least 95% by weight, and most preferably at least 98%
by weight, in each case based on the total weight of the activated
carbon articles. According to a very preferred embodiment, the
activated carbon content in the shaped activated carbon articles is
100% by weight, based on the total weight of the activated carbon
article.
It has been found, surprisingly, that shaped activated carbon
articles having an extremely high content of activated carbon,
preferably containing 95% to 100%, by weight, of activated carbon,
can be produced with good mechanical stability. On account of the
high activated carbon content, the adsorptive capacity of the
shaped activated carbon articles is extremely high.
The activated carbon used is preferably an open-pore activated
carbon having a high content of mesopores. The mesopore volume of
such activated carbons customarily lies in the range of from 0.2 to
1.1 ml/g, the mesopores usually having an average pore size of from
20-300 .ANG. in diameter. For the purposes of the present
invention, activated carbon BAX 1100 from Mead Westvaco Corporation
USA, CNR 115 from Norit Nederland B.V. or activated carbon 1155-2
from German Carbon Teterow GmbH, Germany can be used, for example.
The pore distribution in the shaped monolithic activated carbon
articles is consequently based on the pore distribution in the
types of activated carbon used. Therefore the shaped monolithic
activated carbon articles used in the array of shaped activated
carbon articles according to the invention have a large content of
mesopores. The channels in the shaped activated carbon articles can
have a trigonal, tetragonal, preferably square, pentagonal,
hexagonal, octagonal, round, or oval cross-section. Preferably, the
channels have a round or hexagonal cross-section. Very preferably,
the channel cross-section has a hexagonal geometry.
According to a further preferred embodiment, the array of shaped
activated carbon articles contains at least three shaped monolithic
activated carbon articles whose channels are connected so as to
communicate with one another.
It is furthermore preferred that the free cross-sectional area
formed by the channel cross-sections increases from one shaped
monolithic activated carbon article to the next. That is to say,
the free cross-sectional area formed by the channel cross-sections
increases from the first to the second and from the second to the
third shaped monolithic activated carbon article or to any further
shaped activated carbon article disposed in the array of shaped
activated carbon articles.
Preferably, the free cross-sectional area formed by the channel
cross-sections in consecutive shaped monolithic activated carbon
articles increases in each case by from 5 to 60% and preferably by
from 10 to 50%. These percentages refer in each case to the free
cross-sectional area of the foregoing shaped activated carbon
article formed by the channel cross-sections.
Preferably, the free cross-sectional area formed by the channel
cross-sections in a first shaped monolithic activated carbon
article is from 10% to less than 35%, preferably from 20% to 30%,
these figures referring to the percentage area formed by the
channel cross-sections, based on the total cross-sectional area of
the shaped activated carbon article.
Furthermore, it is preferred that the free cross-sectional area
formed by the channel cross-sections in a second shaped monolithic
article is from 35% to not more than 60%, preferably from 40% to
55% , these figures referring to the percentage area formed by the
channel cross-sections, based on the total cross-sectional area of
the shaped activated carbon article.
It is furthermore preferred that the free cross-sectional area
formed by the channel cross-sections in a third shaped monolithic
activated carbon article is more than 60% to less than 80%,
preferably from 65% to 75%, these figures referring to the
percentage area formed by the channel cross-sections, based on the
total cross-sectional area of the shaped activated carbon
article.
Thus, in the array of shaped activated carbon articles according to
the invention, shaped monolithic activated carbon articles having
different free cross-sectional areas are combined with one another.
When using this array of shaped activated carbon articles, for
example in tank venting, the shaped activated carbon article having
the smallest free cross-sectional area is positioned near to the
pollutant source, for example a motor vehicle tank, whilst on the
side remote from the pollutant source, for example the atmosphere
side of a motor vehicle, that shaped activated carbon article which
has the largest free cross-sectional area is disposed. That is to
say, from the side of a gas emitting or vapor emitting pollutant
source, for example the tank side of a motor vehicle, to the side
remote from the pollutant source, for example the atmosphere side
of a motor vehicle, the free cross-sectional areas formed by the
channel cross-sections in the shaped monolithic activated carbon
articles arranged in the array of shaped activated carbon articles
increases from, say, a first shaped monolithic activated carbon
article to the second such article and from the second to a third
such article, and so on.
It has been found, surprisingly, that the array of shaped activated
carbon articles according to the invention produces an extremely
low pressure drop compared with an activated carbon packing.
Depending on the inflow area used and the length of the array of
shaped activated carbon articles, the pressure drop can be 90% less
than the pressure drop of an activated carbon packing having a
comparable adsorptive capacity. The pressure drop across the array
of shaped activated carbon articles according to the invention, is
consequently markedly lower than that incurred across an activated
carbon packing having a comparable adsorptive capacity. Preferably,
the pressure drop across the array of shaped activated carbon
articles according to the invention is at least 20% lower, more
preferably at least 50% lower, and most preferably at least 70%
lower, than that produced across a conventional activated carbon
packing having a comparable adsorptive capacity.
It has been found, surprisingly, that effective and reliable
adsorption of gaseous or vaporous pollutants, for example
hydrocarbon vapors, can be achieved by means of the array of shaped
activated carbon articles according to the invention. The
cross-sectional diameter of the channels in the shaped activated
carbon articles preferably lies in the range of from 0.1 mm to 7
mm, preferably from 0.5 mm to 4.5 mm, and more preferably from 0.8
mm to 2.2 mm.
The channel walls separating the channels preferably have a
thickness in the range of from 0.5 mm to 10 mm, preferably from 0.8
mm to 5 mm, and more preferably from 1 mm to 3 mm.
The shaped activated carbon article according to the invention thus
shows, on the one hand, good stability, i.e. high mechanical
strength, and, on the other hand, a low pressure drop and an
outstanding adsorptive capacity.
According to a preferred refinement of the invention, the array of
shaped activated carbon articles has a ratio of length to
cross-sectional diameter of at least 3:1, preferably at least 4:1,
more preferably of at least 6:1, and most preferably of at least
8:1. It has been found, surprisingly, that the adsorptive capacity
and the bleeding behavior can be further optimized if the array of
shaped activated carbon articles has a small inflow area and is of
a large length.
Unlike the activated carbon packing customarily used, the array of
shaped activated carbon articles according to the invention makes
it possible to achieve an optimum ratio of length to
cross-sectional diameter without the resulting pressure drop being
unduly high, as would occur with an activated carbon packing.
Preferably, the array of shaped activated carbon articles has an
incremental adsorption capacity of more than 35 g/l between levels
of 5% and 50%, by volume, of n-butane in air. The incremental
adsorption capacity is obtained from the adsorption isotherm
recorded with mixture ratios of n-butane in air by subtracting the
adsorption value at 5% by volume of n-butane from the value at 50%
by volume of n-butane. The value is standardized to a volume of 1
liter. More preferably, each individual shaped activated carbon
article in the overall array has this adsorptive property, i.e. a
system of at least two in-line adsorptive filters (or alternatively
adsorptive volumes) results, each of which has an incremental
adsorption capacity of of more than 35 g/l between levels of 5% and
50% of n-butane in air.
In order to produce the shaped activated carbon articles according
to the invention, carbon particles, binder, liquid phase, and
optionally further auxiliaries are first of all blended to provide
an extrudable composition. The liquid phase used is preferably
water or an aqueous solution. In addition to binders based on
water, the use of non-aqueous or substantially anhydrous binders,
for example those based on pitch, coal tar, charcoal tar, and/or
bitumen, is possible. Further auxiliaries which can be added are,
for example, plasticizers and/or lubricants. A plasticizer can
improve the processability or extrudability of the composition to
be extruded. A lubricant assists the homogeneous dispersion of the
individual constituents during the extrusion of the composition in
the nozzle of the extruder. In addition, local damming effects in
individual channels of the nozzle during extrusion can be avoided
in an extremely advantageous manner by increasing the degree of
internal slip.
The lubricants used can be surfactants or soaps, for example fatty
acids or fatty acid salts, such as stearates, in order to improve
the slip of the composition in the extruder or its mold. A
plasticizer suitable for use is, for example, a cellulose
ether.
Cellulose ethers which can be used are, for example, methyl
cellulose, ethylhydroxyethyl cellulose, hydroxybutyl cellulose,
hydroxybutylmethyl cellulose, hydroxyethyl cellulose, hydroxymethyl
cellulose, hydroxypropyl cellulose, methylhydroxypropyl cellulose,
hydroxyethylmethyl cellulose, sodium carboxymethyl cellulose, or
mixtures thereof.
Binders which have proven very suitable are water-containing
binders. Binders which can be used are, for example, carbohydrates,
starch, sugars, and/or mixtures thereof. Sugars which have proven
very suitable are sugar mixtures, preferably molasses. In addition
to binders based on water, the use of non-aqueous binders, for
example those based on pitch, coal tar, charcoal tar, or bitumen,
is possible.
The carbon particles employed are preferably of coke based on wood,
peat, stone fruit kernels, nutshells, anthracite, or lignite.
Preferably, finely ground charcoals or activated carbon powders
based on wood or coconut shells are employed as carbon
particles.
The shaped monolithic article having channels obtained after
extrusion is preferably cut to desired lengths and subsequently
dried. Drying is preferably carried out in a forced air oven at
approximately 50.degree. C. to approximately 100.degree. C.
However, it is alternatively possible to use other drying methods
such as, for example, microwave techniques. After drying, the
shaped monolithic article preferably has a water content of 25% by
weight or less.
Carbonization of the dried shaped article is preferably carried out
in the range of from approximately 500.degree. C. to 850.degree.
C., preferably at approximately 600.degree. C. to 700.degree. C.
The respective final temperature is maintained until substantially
no more pyrolysis products or decomposition products are given off.
During carbonization, the auxiliaries added, such as, for example,
wax, surfactant, soap, cellulose ether, or starch, are decomposed
and the binder used, such as molasses or tar, is carbonized. The
shaped carbon article obtained after carbonization preferably
consists of carbon, preferably activated carbon, to an extent of
more than 75% by weight, preferably more than 80% by weight, and
more preferably more than 90% by weight. According to another
preferred embodiment, the shaped activated carbon article consists,
after carbonization, of carbon to an extent of at least 95% by
weight, preferably at least 98% by weight, and more preferably 100%
by weight. These percentages by weight are based in each case on
the total weight of the shaped carbon article, preferably the
shaped activated carbon article.
When using an activated carbon as carbon particles, the shaped
article obtained after carbonization does not have to be further
activated. If a non-activated coke is used as the carbon material,
downstream activation must be carried out. This activation can be
carried out in conventional manner. For example, activation of the
shaped article can be carried out at a temperature of from
500.degree. C. to 1000.degree. C., preferably from 700.degree. C.
to 950.degree. C., in an activating atmosphere containing, for
example, from 25% to 35%, by volume, of steam.
In the production of the array of shaped activated carbon articles
according to the invention, at least two shaped activated carbon
articles having different free cross-sectional areas formed by the
channel cross-sections are then arranged such that the channels of
the at least two shaped activated carbon articles are connected so
as to communicate with one another. As mentioned above, the at
least two, preferably at least three, shaped activated carbon
articles can be arranged either abutting one another or at a
distance from one another. It is essential that the vapors or gases
passing through the channels of the first shaped activated carbon
article can subsequently pass into the channels of the second, or
third, or any further shaped activated carbon articles, such that
preferably all pollutants contained in the gases or vapors will be
reliably adsorbed by the array of shaped activated carbon articles
of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is explained below with reference to figures and
exemplary embodiments which, however, are not to be regarded as
restricting the scope of protection of the present invention.
FIGS. 1a)-1c) show various embodiments of the shaped activated
carbon article 2 having channels 1 used in the array of shaped
activated carbon articles according to the invention. In FIG. 1a),
the channels 1 have a hexagonal cross-section, in FIG. 1b) a round
cross-section, and in FIG. 1c) a square cross-section.
FIG. 2 shows the n-butane adsorptive capacities for the shaped
activated carbon articles depicted in Table 1.
FIG. 3 shows the pressure drops as a function of the volumetric
flow rate of an activated carbon packing in a packed bed filter
compared with shaped monolithic activated carbon articles having
different inflow areas.
FIG. 4 is a diagrammatic representation of an array of shaped
activated carbon articles according to the invention.
FIG. 5 is a diagrammatic representation of another embodiment of an
array of shaped activated carbon articles according to the
invention.
FIG. 6 is a diagrammatic representation of an array of shaped
activated carbon articles of the invention combined with an
activated carbon packing or a packed bed filter.
FIG. 7 shows the pressure drop as a function of the volumetric flow
for an activated carbon packing or a packed bed filter in
conjunction with a monolithic auxiliary filter compared with arrays
of shaped activated carbon articles of the invention.
FIG. 8 shows the adsorptive capacity of a shaped monolithic article
having 200 cpsi (cells per square inch) and a free cross-sectional
area of 65% and wall thicknesses of 220 .mu.m.
FIG. 9 shows the adsorptive capacity of a shaped monolithic article
having hexagonal channels and a free cross-sectional area of 27%
and wall thicknesses as in FIG. 10.
FIG. 10 is a diagrammatical representation illustrating the
thicknesses of the walls situated between the hexagonal
channels.
DETAILED DESCRIPTION OF THE INVENTION
EXAMPLES
The adsorptive capacity or the adsorptive capacity and the pressure
drop of various activated carbon filters were compared with one
another.
Various activated carbon filters are listed in Table 1, which lists
the production process, the activated carbon content, and the
adsorptive capacity for n-butane for each filter.
TABLE-US-00001 TABLE 1 Adsorptive capacity for n- Active carbon
butane, Production content g/100 ml of 50% process % by weight
Filter geometry n-butane Filter 1 original CNR115 100% Packed bed
11.0 from Norit Nederland B.V. Filter 2 DE 10213016 48% Monolith
with 27% open 5.2 area, 52 mm in diameter, 100 mm in length Filter
3 DE 10104882 70% Monolith with 27% open 8.5 area, 52 mm in
diameter, 100 mm in length Filter 4 DE 10003660, 100% Monolith with
27% open 11 extrusion to a area, 52 mm in diameter, monolith
instead of 100 mm in length pressing to shaped carbon
Filter 1 is an activated carbon packing of activated carbon CNR 115
from Norit Nederland B.V., Netherlands. The activated carbon CNR
115 has an average particle size of 2 mm. The cylindrical packed
bed had a length of 100 mm and a diameter of 30 mm and consisted of
100% by weight activated carbon. The inflow area was 7
cm.sup.2.
Filter 2 was produced according to the production process described
in DE 102 13 016 and contained, in addition to 48% by weight of
activated carbon, the following constituents: 42% by weight of
vitrified carbon (carbonized phenolic resin), 7.5% by weight of
fireclay, and 2.5% by weight of silicate.
The cylindrical filter had a diameter of 52 mm and a length of 100
mm. The through channels extending along the longitudinal axis of
the filter had a channel diameter of 1.4 mm and exhibited a
hexagonal cross-section. The free cross-sectional area formed by
the channel cross-sections was 27%. The inflow area was 21
cm.sup.2.
Filter 3 was produced according to the production process described
in DE 101 04 882 and contained, in addition to 70% by weight of
activated carbon, the following constituents: 14% by weight of
vitrified carbon (carbonized phenolic resin) and 16% by weight of
clay. The dimensions of this filter are exactly the same as those
of filter 2.
Filter 4 is a honeycomb article which likewise has the same
dimensions as filter 2. Instead of using the formulation according
to DE 102 13 016, however, the formulation as is described in WO
00/78138 A2 for the extrusion of 1 mm shaped activated carbons, is
used. The extruded green molding is carbonized after drying at
550.degree. C. and then immediately activated with steam at
850.degree. C.
As can be seen from Table 1, filter 4 has an adsorptive capacity
for n-butane comparable to that of Filter 1.
The pressure drop determined for various filter types is listed in
Table 2 below.
TABLE-US-00002 TABLE 2 Inflow area, Pressure drop at Filter
cm.sup.2 Depth, cm 70 l/min Packed bed 21 10 689 Pa Monolith with
27% free 21 10 63 Pa cross-sectional area Monolith with 27% free 21
20 115 Pa cross-sectional area Monolith with 27% free 10.5 20 231
Pa cross-sectional area Monolith with 27% free 7 30 560 Pa
cross-sectional area
The pressure drop was in this case measured according to DIN
71460-1 in a flow channel having a diameter of 80 mm and at a
volumetric flow rate of 70 l/min
As can be seen from Table 2, the pressure drop produced by a shaped
monolithic article having the same inflow area and depth and a free
cross-sectional area of 27% formed by its channel cross-sections is
only approximately 10% (63 Pa) of the pressure drop (689 Pa)
produced by an activated carbon packing (packed bed of activated
carbon) having the same external dimensions. On doubling the depth
to 20 cm and keeping the same inflow area of 21 cm.sup.2, the
pressure drop produced by a shaped monolithic article having 27%
free cross-sectional area is only approximately 16% of the pressure
drop produced by an activated carbon packing having the same inflow
area and a depth of 10 cm. Even on halving the inflow area of a
shaped monolithic activated carbon article having a free
cross-sectional area of 27% to 10.5 cm.sup.2 and a depth of 20 cm,
the pressure drop is still significantly lower than in the case of
an activated carbon packing having an inflow area of 21 cm.sup.2
and a depth of 10 cm. The pressure drop across the aforementioned
shaped monolithic activated carbon article is only approximately
30% of the pressure drop across the said activated carbon
packing.
Even with a further reduction in the inflow area to 7 cm.sup.2 and
an increase in the depth to 30 cm, the pressure drop is still lower
than that produced by an activated carbon packing having an inflow
area of 21 cm.sup.2 and a depth of 10 cm.
From a comparison of the data listed in Table 1 and Table 2, it
will be seen that a shaped monolithic article having an activated
carbon content of 100% by weight has a similar n-butane adsorptive
capacity to that of an activated carbon packing having an activated
carbon content of 100% by weight, whilst the pressure drop across a
shaped monolithic activated carbon article is significantly lower
than that produced by an activated carbon packed bed.
The data on n-butane adsorptive capacity listed in Table 1 are
shown graphically in FIG. 2 in the form of a bar chart.
In FIG. 3, the measured curves of the pressure drop across each of
the activated carbon filters indicated in Table 2 are plotted as a
function of the volumetric flow rate. The volume of all activated
carbon filters was in each case 210 cm.sup.3, with the exception of
the shaped monolithic article, which had an inflow area of 21
cm.sup.2 and a depth of 20 cm and consequently a volume of 420
cm.sup.3.
FIG. 3 clearly shows that the pressure drop across monolithic
shaped activated carbon articles is significantly lower than that
incurred across an activated carbon packing (curve "Bed CNR 115"
.box-solid.). Even on doubling the depth of a shaped monolithic
activated carbon article, i.e. by doubling the volume (curve:
"double volume" .tangle-solidup.), the pressure drop is only
insignificantly higher than the pressure drop incurred across an
activated carbon packing. By increasing the depth of a shaped
monolithic activated carbon article, the diffusion length for
gaseous or vaporous pollutants, for example hydrocarbons escaping
from a motor vehicle tank, is consequently also increased. On
doubling the depth of a shaped monolithic activated carbon article,
the diffusion length for the gaseous or vaporous pollutants, for
example hydrocarbons, is also doubled. By increasing the depth of
the shaped monolithic activated carbon article or by increasing the
diffusion length, the evaporative emissions of, for example
hydrocarbons, from a partially loaded filter can be advantageously
reduced. By reducing the inflow area and increasing the flow path,
for example by reducing the inflow area by two thirds and tripling
the depth of the shaped monolithic activated carbon article, i.e.
by tripling the flow path, the evaporative emissions of pollutants,
for example hydrocarbons, can be reduced still further. As can be
seen from FIG. 3 (curve "one third inflow area" .star-solid.), such
optimization of the shaped monolithic activated carbon article
results in a pressure drop which is still lower by approximately
20% than that incurred across the activated carbon packing referred
to for comparison.
Surprisingly, it has now been found that the reduction in the
evaporative emissions and the regenerability can be further
optimized by means of the array of shaped activated carbon articles
of the invention.
FIG. 4 is a diagrammatic representation of an array of shaped
activated carbon articles according to the invention. The shaped
monolithic activated carbon articles 2', 3' and 4' are arranged in
succession, for example in a housing 7'. The housing 7' can, for
example, be one made of plastic, stainless steel, a film or foil,
or a shrinkage tube. The array of shaped activated carbon articles
is in this case linked via the connection 1' to the pollutant
source, for example a tank filled with motor fuel. The openings 5'
and 6' are the outlets to the atmosphere or to the environment. The
pollutants, for example hydrocarbons, emitted from a tank or motor
vehicle, consequently enter the array of shaped activated carbon
articles of the invention via connection 1'. The free
cross-sectional area formed by the channel cross-sections
preferably increases in this case from the shaped monolithic
activated carbon article 2' to the shaped monolithic activated
carbon article 3' and from the latter to the shaped monolithic
activated carbon article 4'. For example, the free cross-sectional
area of the shaped monolithic activated carbon article 2' shown in
FIG. 4 can be barely less than 35%. The free cross-sectional area
of the shaped monolithic activated carbon article 3' formed by the
channel cross-sections can, for example, be between 35% and not
more than 60%. The free cross-sectional area of the shaped
monolithic activated carbon article 4' formed by the channel
cross-sections is preferably more than 60%, for example 70%.
FIG. 5 shows another preferred embodiment of the array of shaped
activated carbon articles of the invention. In this refinement of
the array of shaped activated carbon articles according to the
invention, two shaped monolithic activated carbon articles 2''' are
disposed parallel to one another. The shaped monolithic activated
carbon articles 3''' and 4''' are arranged in line, the array
consisting of the shaped monolithic activated carbon articles 3'''
and 4''' being parallel to the shaped monolithic activated carbon
articles 2'''. The gaseous or vaporous substances, for example
hydrocarbons, pass through the connector 1''' into the first shaped
monolithic activated carbon article 2'''. At the end of the first
shaped monolithic activated carbon article 2''', the unadsorbed
pollutants then pass into the second shaped monolithic activated
carbon article 2''' and subsequently into the downstream monolithic
shaped activated carbon articles 3''' and 4'''' before the gases or
vapors safeguarded from pollutants are emitted to the environment
or atmosphere via the outlets 5''' and 6'''. The dual arrangement
of the first shaped monolithic activated carbon article 2''' leads
to a marked improvement in the reduction of residual emissions of
pollutants to the environment. As can be seen from FIG. 3, doubling
the length of the shaped monolithic activated carbon article 2''',
i.e. doubling the diffusion path, leads to only an insignificant
increase in the pressure drop.
Regarding the increase in the free cross-sectional area of the
shaped activated carbon articles 2''' through 3'''' to 4''' formed
by the channel cross-sections, reference is made to the statements
referring to FIG. 4.
FIG. 6 depicts another possible embodiment of the present
invention. The array of shaped activated carbon articles of the
invention can be combined with a conventional activated carbon
packing. In this arrangement, the array of shaped activated carbon
articles according to the invention is downstream of the activated
carbon packing. The gaseous or vaporous pollutants, for example
hydrocarbons, pass through the connector 1'''' into the activated
carbon packing 8''''. The residual pollutants escaping from the
activated carbon packing 8'''', for example hydrocarbons, then
enter into the array of shaped activated carbon articles according
to the invention. The activated carbon packing 8'''' can in this
case be arranged parallel to the shaped monolithic activated carbon
article 3'''' for space optimization. The remaining pollutants
escaping from the shaped monolithic activated carbon article 3''''
then enter into the shaped monolithic activated carbon article
4''''. The gases or vapors deplete of pollutants, preferably
hydrocarbons, are then emitted to the environment or atmosphere via
the outlets 5'''' or 6''''. The shaped monolithic activated carbon
articles 3'''' and 4'''' are preferably likewise arranged parallel
to one another. Regarding the increase in the free cross-sectional
area formed by the channel cross-sections, reference is made to the
statements referring to FIG. 4.
The parallel arrangement of shaped monolithic activated carbon
articles, optionally in conjunction with an activated carbon
packing, allows for a highly advantageous compact construction in a
housing 7''''. The array of shaped activated carbon articles
according to the invention, optionally in conjunction with an
activated carbon packing, can be placed in any suitable housing.
Preferably, this housing is manufactured from pollutant-resistant
plastics material.
FIG. 7 depicts the pressure drop incurred across various
arrangements of activated carbon filters at different volumetric
flow rates. Table 3 lists the lengths and free cross-sectional
areas of the various arrangements of activated carbon filters
used.
TABLE-US-00003 TABLE 3 Additional filter Additional filter 31
channels/cm.sup.2 62 channels/cm.sup.2 Main filter Open area: 60%
Open area: 70% Inflow Depth Inflow area Depth Inflow area Depth
Pressure Main filter area cm.sup.2 cm cm.sup.2 cm cm.sup.2 cm drop
Packed bed 21 10 -- -- 689 Packed bed 21 10 7 10 -- 789 Monolith 21
20 7 10 332 with 27% open area Monolith 10.5 20 10.5 5 10.5 5 384
with 27% open area
In FIG. 7, no pressure drop curve is shown for the activated carbon
packing having an inflow area of 21 cm.sup.2 and a depth of 10 cm
listed in Table 3. In Table 3, for purposes of comparison, the
pressure drop is only indicated at a volumetric flow rate of 70
l/min. It is evident from FIG. 7 that the pressure drop produced
across an activated carbon packing and a downstream shaped
monolithic activated carbon article (curve A) having a free
cross-sectional area of 60% with 31 channels per cm.sup.2 is
significantly greater than that produced across the two arrays of
shaped activated carbon articles comprising two (curve B) or three
(curve C) shaped activated carbon articles. Curve B was determined
using an array of shaped activated carbon articles according to the
invention consisting of a first shaped activated carbon article
having an inflow area of 21 cm.sup.2, a depth of 20 cm and a free
cross-sectional area of 27% (25 channels/cm.sup.2) in conjunction
with a second shaped activated carbon article, which has an inflow
area of 7 cm.sup.2, a depth of 10 cm and a free cross-sectional
area of 60% providing 31 channels per cm.sup.2. Curve C was
measured on an array of shaped activated carbon articles according
to the invention comprising a first shaped activated carbon article
having an inflow area of 10.5 cm.sup.2, a depth of 20 cm and a free
cross-sectional area of 27% (25 channels/cm.sup.2) in conjunction
with a second shaped activated carbon article having an inflow area
of 10.5 cm.sup.2, a depth of 5 cm and a free cross-sectional area
of 60% (31 channels/cm.sup.2) and a third shaped activated carbon
article having an inflow area of 10.5 cm.sup.2, a depth of 5 cm and
a free cross-sectional area of 70% (62 channels/cm.sup.2).
The activated carbon packing and the shaped monolithic activated
carbon article used in each case consisted of 100% by weight
activated carbon. The activated carbon in the activated carbon
packing had a particle size of 2 mm. In the filter arrays measured,
the main filter (packed bed or shaped monolithic activated carbon
article in each case having a free cross-sectional area of 27%) and
the additional filters were arranged in succession. The volume to
be filtered flowed through the filter arrays traversing the main
filter and the first and second additional filters in that
order.
It has been found that a combination of an activated carbon packing
(packed bed) with a shaped monolithic activated carbon article
having a free cross-sectional area of 70% results in a greater
pressure drop than a combination of an activated carbon packing and
a shaped monolithic activated carbon article having a free
cross-sectional area of 60%. The reason for the increased pressure
drop when use is made of a monolithic shaped activated carbon
article having a free cross-sectional area of 70% in conjunction
with an activated carbon packing is due to the greater air friction
caused by the larger number of channels per cross-sectional area.
Thus the overall pressure drop across an activated carbon packing
in conjunction with a shaped monolithic activated carbon article
having a free cross-sectional area of 70% is too large. It is
evident from FIG. 7 that the pressure drop across an array of
shaped activated carbon articles comprising three shaped monolithic
activated carbon articles having free cross-sectional areas of 27%,
60% and 70% respectively is significantly lower than the pressure
drop across an activated carbon packing in conjunction with a
shaped activated carbon article having a free cross-sectional area
of 60%.
In FIG. 8 and FIG. 9 the regenerability of shaped monolithic
articles is shown as a function of the cell content (cpsi=cells per
square inch). The use of the unit cpsi provides a measure of the
number of channels per cross-sectional area. FIG. 8 illustrates the
adsorptive capacity of a shaped monolithic article having 200 cpsi
and a free cross-sectional area of 65% as formed by the channel
cross-sections. The wall thicknesses between the channels having a
square channel cross-section were 220 .mu.m. The channels had a
cross-sectional area of 1.3 mm.times.1.3 mm.
FIG. 9 illustrates the regenerability of a shaped monolithic
article having a free cross-sectional area of 27% as formed by
channel cross-sections. The hexagonal channel cross-section had a
channel diameter of 1.4 mm. The wall thicknesses between the
channels having a hexagonal cross-section were between 1 and 2 mm,
as may be seen from FIG. 10.
FIG. 8 and FIG. 9 indicate, respectively, the relative filter load,
based on the first load, on the ordinate axes. In the filter used
for the determination of the adsorption and desorption behavior
shown in FIG. 9, the absolute adsorptive capacity is of course
greater than in the filter which was used to obtain the readings
shown in FIG. 8. From the comparison of the adsorption and
desorption values shown in FIG. 8 and FIG. 9, it is evident that
the monolithic filter having wall thicknesses between 1 mm and 2 mm
used in FIG. 9 has an adsorption and desorption behavior comparable
to a monolithic filter having a wall thickness of 220 .mu.m.
The working capacity or adsorptive capacity test and the power to
release the adsorbed hydrocarbons by regeneration with air was
determined using a test based on ASTM D 5228-92. The corresponding
shaped article was loaded with n-butane, loading with a
concentration of 50% of n-butane in nitrogen being carried out at a
volumetric throughput rate of 0.1 l/min up to a breakthrough of
5000 ppm. Subsequently, desorption was carried out using 22 l/min
of dry air over a period of 15 minutes. Several
adsorption/desorption cycles were investigated.
The person skilled in the art would have expected that a monolithic
filter having markedly thicker wall thicknesses, i.e. wall
thicknesses of a number of millimeters, would show a significantly
poorer desorption behavior. As is evident from FIG. 8 and FIG. 9,
the adsorption and desorption behavior both of the monolithic
filter having a free cross-sectional area of 65% and of a
monolithic filter having a free cross-sectional area of 27% is
between 70 and 80%, in each case based on the first filter
load.
The progressive construction employing honeycomb articles having a
small open area on the tank side and honeycomb articles having a
large open area on the atmosphere side causes a stepped capacity
for hydrocarbons. There is a high capacity on the tank side, and
low capacity on the atmosphere side. This construction ensures that
even at very low flushing rates, e.g. after a very short journey
following filling up with fuel, those filters of the filtering
system which are situated on the atmosphere inside will always be
flushed free and thus will always have a free adsorption capacity
for bleeding emissions.
The inventors have consequently found, surprisingly, that a
monolithic activated carbon filter having a large absolute
adsorptive capacity, i.e. having a low free cross-sectional area
formed by the channel cross-sections of, for example, only 27% and
correspondingly large wall thicknesses, which, for example, can be
between 1 mm and 2 mm, has a regenerability comparable to that of a
packed bed. Unlike a packed bed, however, the pressure drop is
significantly lower.
Consequently, the array of shaped activated carbon articles
according to the invention provides an efficient filter unit which
has, on the one hand, a high adsorptive capacity and, on the other
hand, a small pressure drop across the entire array of shaped
activated carbon articles. Since the array of shaped activated
carbon articles according to the invention preferably has a shaped
monolithic activated carbon article having the greatest free
cross-sectional area on the waste air side, i.e. the side facing
the atmosphere or the side remote from the pollutant source, the
adsorbed pollutants, for example hydrocarbons, can easily be
desorbed by flushing with air in the reverse direction.
When using the array of shaped activated carbon articles according
to the invention as a tank venting system in a motor vehicle, the
array of shaped activated carbon articles according to the
invention is flushed in the reverse direction when the motor
vehicle is operated. That is to say, the air is sucked in from the
environment through the array of shaped activated carbon articles
according to the invention such that the adsorbed pollutants,
preferably hydrocarbons, are flushed back into the engine of the
motor vehicle for combustion therein. On operation of the motor
vehicle, the array of shaped activated carbon articles loaded
during idle periods of the motor vehicle is thus regenerated.
Thus the object underlying the invention is also achieved by the
provision of a tank venting system which contains an array of
shaped activated carbon articles as proposed by the invention. The
array of shaped activated carbon articles according to the
invention is consequently suitable for use in a tank venting
system.
The object of the invention is additionally achieved by a motor
vehicle which contains an array of shaped activated carbon articles
according to the invention or a tank venting system according to
the invention. The array of shaped activated carbon articles
according to the invention and the tank venting system according to
the invention are consequently suitable, in particular, for use in
motor vehicles.
* * * * *